The present invention pertains to a method for aligning an arrangement for marking of directions for perforating together with a position determining arrangement, attached to a machine with a movable arm, in bone structures at surgery, and to said arrangements.
Present methods regarding, for example, hip fracture surgery involves a great deal of craftsmanship. A patient with an injured leg is placed supine on a fracture table and a reduction maneuver is carried out. The foot of an injured leg is firmly fixed in a specially built shoe. Traction and rotation are applied until the fracture is reduced.
A fixation of an injured leg is normally so firm that no movement will take place unless a substantial force is applied to the leg. A mobile X-ray apparatus, a xe2x80x9cC-armxe2x80x9d, with two perpendicular radiographs, the anteroposterior (AP) and the lateral (Lat) projections, checks quality of reduction. The result of a reduction can only be judged through said at least two radiographs, and no correction for variations in hip rotation is possible.
Screws are inserted in order to fixate the fractured bone parts. The screws are introduced by a hand-held drill which opens up guide holes for the screws, whereby a surgeon has to judge the position of the drill from said two perpendicular radiographs and manually adjust the position of the drill in three dimensions, which is a very difficult task.
Unfortunately, the insertion of screws very often has to be repeated. Repeated trials of insertion destroy the bone structure in the femoral neck.
To be able to check the quality after a performed hip fracture surgery a method was developed for determining the post surgery position of a fixating means. It was introduced by the inventor of the present invention in his thesis xe2x80x9cInternal Fixation of Femoral Neck Fracturesxe2x80x9d, Stockholm 1993, ISBN 91-628-0804-4. Nevertheless, the method has only been used for post-surgery quality checks and scientific statistics, and it has not occurred to or been obvious to any person skilled in the art to modify the method so it can be used in determining how and where to drill in a femoral bone fracture in order to attach fixating means and facilitate healing of said fracture in a best possible way.
Today, orthopedic surgery has promulgated towards sophisticated hi-tech implants being manually inserted through in-precise techniques. To manually insert implants is a task for a highly skilled orthopedic surgeon with, for example, 10 years of training in the present medical field.
For diagnosis groups, where a great number of injuries is accumulated, the result of performed surgery is less satisfactory than it could be. Hip fractures belong to such a group, hereby about 18,000 incidents/year occur in Sweden alone, 9.000 cervical and 9,000 pertrochanteric, to a cost of approximately SEK 1.4 billions.
Despite of the more than 100 different fixating methods developed for this kind of fractures, the result of performed surgery is relatively poor. As much as approximately 35% of all cervical fractures do not heal, and 20% of them have to be re-operated within a time period of 1-2 years. For pertrochanteric fractures the same rates are 10% and 4% respectively. Every re-surgery approximately costs SEK 185.000.
It is agreed with among surgeons and other experts that the main reason for the high percentage of re-surgery is an inadequately positioning of the fixating screws, which hold the fracture together during the following healing process, see xe2x80x9cFixation of femoral neck fractures: comparison of the Uppsala and Von Bahr screws.xe2x80x9d By Rehnberg and Olerud, Acta Orthop Scand 60, 1989, p. 579-584.
Considering the costs of SEK 185.000 for one re-surgery, a decrease in the rate of such surgery with 50% would gain a save of SEK 160 millions in Sweden a year in surgery costs. A bigger Swedish Hospital would save approximately SEK 8 millions, not to say what is gained in relief for fractured patients.
A known arrangement to support surgery is the so-called ROBODOC(trademark) Surgical Assistant System. The ROBODOC(trademark) robot is able to precisely prepare a femoral channel for placement of a cementless prosthesis.
Due to the manual surgery technique involved in surgery relating to bone fractures and judgements made from said radiographs in real time during surgery/surgical treatment without any tools for performing analysis, the X-ray radiation will be unnecessary high for patients and personnel serving during surgery.
From U.S. Pat. No. 5,603,243 by Finley, an alignment apparatus for aligning X-ray images is known. The apparatus comprises two elongate members in an orthogonal configuration in relation to each other on a supporting framework. Within each member there are four predetermined axes with a plurality of balls mounted on each axis. The balls are preferably of different sizes or are designed to absorb different quantities of X-ray radiation, so that the images of the balls may be recognised individually on an X-ray plate. Since the orientation and spacing of the balls is known, it is possible to determine the precise position and precise orientation of parts of a patient present within an X-ray image through calculation.
The support frame and the elongated members with axes comprising balls provides a fairly complicated apparatus with a lot of calculations for alignment of X-ray images, thus an alignment method or apparatus of simpler construction would be appreciated.
It would be an advantage therefore, to provide a method and arrangements that can aid a surgeon in preparing and supporting orthopedic surgery. Such a method and arrangements are set forth through attached independent claims. Specific embodiments of the invention are introduced through the attached dependent claims. Hence, the method and arrangements of the present invention and details thereof provides such advantages.
The present invention aims to solve problems related to determining positions, directions and distances in magnified X-ray images for bone structure surgery.
In order to solve said problems, the present invention sets forth a method for aligning a means for marking of directions for perforating together with position determining means, attached to a machine with a movable arm, in bone structures at surgery, comprising the following steps:
attaching a marking pin to said means for marking, activating said machine and move said means for marking to a defined start position;
assigning said machine a first operation position changing its co-ordinate system so that movement of the marking pin is, approximately, performed within the cross-section of a movable marking pin holder;
aligning said position determining means in relation to said means for marking, said position determining means having at least four round elements;
positioning said position determining means vertical to a reference surface, adjusted so that the marking pin points in a direction, which axis coincides with each round element when the machine moves a specified distance in a square pattern;
placing said position determining means adjacent to the part of the body where the perforation is to be made;
placing an X-ray machine adjusted so that, when radiographs are taken, two of said four round elements cover each other in two orthogonal projection planes;
determining a starting position, whereby said two covered round elements represent the starting position for the machine;
digitizing said radiographs and using the distances between said other non covered round elements in said radiographs, representing the magnification factor, which is calculated and displayed, whereby the magnification factor relates to the movement of the machine arm;
introducing said marking pin through skin and muscles to a position close to the bone structure which is to be perforated;
measuring the distance the marking pin holder has to be moved, thereby giving the machine a second operation position in accordance with the distance the marking pin holder has been moved, whereby the machine arm is able to move around this second position even if the pin and second cylinder is removed, thus all machine movements can take place outside a patients body, but the center of movements will still be close to the bone inside the patients body;
measuring the position of the Marking steel pin, and the lenght to a predetermined marker on said marking pin out off said digitized radiographs, calculating a scale factor for the position of the marker;
marking a desired position for a perforation means in the bone on said digitized radiographs;
comparing a desired position for said perforation means in the bone with the actual position for said marking pin;
making corrections for magnification and scale;
calculating distances and angles that said machine has to move its arm in order to align the marking pin with the perforation position in the bone;
automatic repositioning of the machine in accordance with said calculated distances and angles; and
through said machine, performing a perforation of the bone.
In one embodiment the marking pin is changed to a perforator, held by a similar pin holder, said perforator being suitable for drilling, screwing, pinning, milling, grinding or threading.
In another embodiment, a chosen perforator is advanced, by means of said pin holder, so that it enters through the skin and muscles to a position close to the bone.
In a still further embodiment a checking procedure is performed by marking and outlining the direction and position of the perforator and comparing it with the marked perforator position. If the trajectory of the perforator deviates more than a specified distance from the marked desired position, the positioning procedure is redone from the present position, considerably reducing the distances the machine has to move, and therefore reducing positioning errors.
Another embodiment of the present invention comprises that said pin holder is slide-able, and that it is provided in different dimensions with different sizes of a central hole for fitting of marking pins and perforators.
In order to be able to accomplish the aims of the present invention two means are part of the invention.
According to the invention a means for marking of directions and holding of tools for perforation in bone structure surgery, for attachment to a machine with a movable arm is set forth It comprises an outer casing with an aperture for holding an inner casing, one of said casings being slide-able in relation to said movable arm, said inner casing having an attachment for holding perforation means. It is attached to a turnable support or a turnable and tiltable support on said machine.
In one embodiment the slidable casing is electrically actuated to move back and forth.
Another embodiment comprises that one of said casings is revolving for drilling, grinding, milling or other movement used during perforation.
A still further embodiment encompasses that the attachment is able to fit a machine for drilling, grinding, milling or other movement used during perforation.
According to the invention a position determining means used for finding directions for perforation in bone structure surgery, attached to a machine with a movable arm is set forth. It is provided with a first plate and a second plate, both plates being substantially transparent to X-ray radiation in an orthogonal direction, and mounted in an orthogonal configuration, said first plate being provided with four round elements, said second plate being mounted on a turnable and tiltable support for attachment to said machine or initially attached, whereby an X-ray magnification factor relating to two orthogonal X-ray radiographs, comprising the round elements, taken of the bone structure is determined when two of said round elements cover each other in both radiographs, said magnification factor being determined by the distance between said two uncovered round elements and dependent on the movement of said machine arm.
In one embodiment of the position determining means according to the present invention a turn-able support is mounted on a movable frame of said machine, whereby it can be placed in front of means for marking of directions and holding of tools for perforation on said machine.
In another embodiment of the invention the round elements are opaque to X-ray radiation. The round elements are made out of materials opaque to X-ray radiation such as tantalum, lead, steel etc alloys of said materials.
In a preferred embodiment of the invention said round elements are placed in a square configuration on said first plate.